Sanding machine



March 10, 1959 R. F. PENDERGAsv-T 2,876,600 SANDING MACHINE." I

3 Sheets-Sheet'l Filed Aug. 15, 1956 v INVENToR.

faF/VZYJ March 1o, 1959 A Filed Aug. 15, 1956 R. F. PENDERGAST SANDING MACHINE n 3 Sheets-Sheet 2 INVENTOR.

` Y BY m Afro/@wirf March 10, 1959 R. PENDERGAs-T 2,876,600

' SANDING MACHINE Filed Aug. 15, 195es sheets-Sheet' s SANDING MACHINE Raymond F. Pendergast, Robbinsdale, Minn. Application August 13, 1956, Serial No. 603,485

2 Claims. (Cl. 51139) My invention relates generally to sanding machines, -and more particularly to such machines utilizing a wide endless sanding belt entrained over a pair of spaced rolls and traveling at high speed to sand or otherwise treat a generally at surface of a workpiece fed through the machine.

. An important object of my invention is the provision of a sanding machine employing a power-driven feed roller, a power-driven contact roll in opposed relation to the feed roller, an idler roll, a sanding belt entrained over said contact and idler rolls, a novel means for mounting said rolls for movement of said contact roll toward and away from the feed roller and an interposed workpiece, whereby the contact roll will follow longitudinal varia tions in the contour of the belt engaged surface of the work -piece during travel thereof through the machine.

Another object of my invention is the provision of a machine as set forth, in which the Contact roll is yieldingly biased toward engagement with a workpiece being moved by the feed roller, and of novel means for varying the yielding bias applied to said contact roll whereby to accurately control the sanding action of the sanding belt upon the workpiece.

Still another object of my invention is the provision of a machine of the above type having a base frame and va rocking frame mounted on the base frame for rocking movements relative thereto, said rocking frame carrying the contact roll and idler roll, the contact roll overlying the feed roller and movable toward and away from the feed roller under rocking movement of the rocking frame, and of a shiftable control element movable in opposite directions to cause bodily movement of the contact roll toward or away from the feed roller.

t Another object of my invention is the provision of novel supporting means for said rocking frame and com-- prising primary and secondary pivot shafts respectively lat opposite sides of the rocking frame, the secondary shaft being releasably connected to one of said frames and removable therefrom to permit entrainment of the sanding belt over the contact and idler rolls.

Another object of my invention is the provision of a sanding machine as set forth having novel means for automatically and accurately maintaining the sanding belt against lateral creep relative to the contact and idler rolls over which the same is entrained, when running at high speed and under a work load.

Another object of my invention is the provision of a sanding machine of the type herein disclosed which is relatively simple and inexpensive to manufacture, which is highly efficient in operation, and which is rugged in construction and durable in use.

The above and still further highly important objects and advantages of my invention will become apparent from the following specification, appended claims, and attached drawings.

, Referring to the drawings, which illustrate the inven tion, and in which like reference characters indicate like parts throughout the several views:

, United States Patent y 2,876,600 Patented Mar. 10, 195.9.

Fig. 1 is a view in side elevation of a sanding machine built in accordance with my invention, some parts being broken away and some parts shown in section;

Fig. 2 is a view in top plan of the machine of Fig. 1, some parts being broken away;

Fig. 3 is a view in end elevation as seen from the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary section taken sub stantially on the line 4-4 of Fig. 1; and

Fig. 5 is an enlarged fragmentary detail in section, taken substantially on the line 5-5 of Fig. 1.

Referring. with greater detail to the drawings, the numeral 1 indicates, in its entirety, a relatively stationary or fixed base frame comprising, a base plate 2, a pair of elongated opposed side frame members 3 and 4, and front and rear-end frame members 5 and 6 respectively. Preferably, and as shown, the side frame members 3 and 4 are of greater heightythan the end frame members 5 and 6, and have journaled therein diametrically reduced shaft end portions of a plurality of workpiece supporting rolls which support a workpiece X during its travel through the machine' from the front to the rear-end thereof. A pair of such supporting rolls disposed toward the front end of the machine are indicated by the numerals 7 and 8, and are provided with reduced shaft portions 9 that are journaled in the side frame members 3 and 4.

' Other supporting rolls toward the rear end of the machine are indicated at 10 and are provided with diametrically reduced shaft portions 11 that are journaled in the side frame members 3 and 4 in the same manner as the shaft portions 9 of the forward supporting rolls 7 and 8. As will hereinafter fully appear, the work supporting rolls 7 and 8 are power-driven to assist in feeding the workpiece X through the machine. With reference to Figs. l and 4, it will be seen that the shaft portions 9 of the rolls 7 and 8 extend laterally outwardly with respect t0 the side frame member 4, and are provided at their outer ends with pulleys 12 by means of which the same are power-driven. A pair of work-engaging hold-down or pressure rolls 13 are disposed in overlying spaced relation, one each to one of the rolls 7 and 8, and are provided at their opposite ends with diametrically reduced shaft portions 14 that are mounted for rotary and vertical movements in slots 1S of upwardly extending pairs of brackets 16 and 17, one each of which is welded or otherwise secured to the upper edge of each of the side frame members 3 and 4. The brackets 16 and 17 are of hollow construction, each containing a shoe 18 which engages and forms a journal for an adjacent shaft portion 14 of its respective pressure roll 13, and a cap element 19 in upwardly spaced relation thereto. Coil compression springs 20 are interposed one each between each shoe 18 and its overlying cap element 19. An adjustment screw 21 is screw threaded in and extends downwardly to the interior of each bracket 16, each screw 21 engaging a respective cap element 19, whereby to provide for variable spacing between the rolls 7 and 8 and their respective overlying pressure rolls 13. The springs 18 permit limited vertical movement of the pressure roll 13 whereby to allow a workpiece X having slight variations in thickness between its opposite ends, to pass therebetween. Preferably, the feeding and supporting rolls 7 and 8 as well as the rolls 10 and 11 and the pressure rolls 13, are made from steel or like rigid material, whereby the workpiece X is rigidly supported during the sanding operation as will hereinafter become apparent.

Disposed between the rolls 7 and 8, and in parallelv ment thereto from the front toward the rear end of tht;A

base frame 1. The opposite ends of the core 23 are diametrically reduced to provide shaft portions 25 and 26, the former of which is suitably iournaled in the side frame member 3, the latter being likewise journaled in the side frame member' 4. The feed roller 22 is driven by a motor 27, preferably of the type having a built-in speed reduction gearing, not shown, and transmission mechanism including a pulley 28 rigidly secured to the output shaft 29 of the motor 27, and an endless drive belt 3i) running over the pulley 28 and another pulley 31 fast on the shaft portion 26 of the feed roller 22, see particularly Fig. 3. A pair of pulleys 32, one of which is shown in Fig. l, are secured fast on the outer end of the shaft portion 26 outwardly of the adjacent side frame member 4, and are utilized to drive the rollers '7 and 8 through the medium of a pair of endless belts 33 and 34, one each running over one of the pulleys 32 and a respective one of the pulleys 12.

Disposed in overlying relation to the xed base frame 1 is a generally rectangular rocking frame, indicated in its entirety by the numeral 35, andV comprising, a pair of laterally spaced parallel side elements 36 and 37 which are generally horizontally disposed, and which extend generally longitudinally of the base frame 1, a cross bar 38 and transverse brace bars 39 and 40. The cross bar 38 is preferably welded at its opposite ends to the side elements 36 and 37 adjacent the rear ends thereof, while the brace bars 39 and 40 are bolted or otherwise rigidly secured at their opposite ends to the intermediate portions of the side elements 36 and 37. A relatively large diametenpreferably rubber covered, contact roll 41 is disposed between the front end portions of the side elements 36 and 37 of the rocking frame 35, and is provided at its opposite ends with reduced diameter shaft portions 42 and 43 which are respectively journaled in the side elements 36 and 37. The contact roll 41 is disposed in opposed overlying spaced parallel relation to the powerdriven feed roller 22, see particularly Fig. 1. At the rear end portion of the rocking frame 35, `an idler roll 44, of considerably less diameter than the contact roll 41, is disposed in substantially parallel relationship to the contact roll 41. The idler roll 44, at its opposite ends, isprovided with axially extending reduced diameter shaft portions 45 that are iournaled in supporting arms 46 at opposite ends of a bifurcated mounting element or yoke 47. The yoke 47 is mounted on the cross bar 38, for pivotal swinging movements about a generally vertical axis, by means of a pivot bolt or the like 48 that is screw threaded into the cross bar 38. The intermediate portion of the yoke 47 is provided with an arcuate slot 49 concentric with the axis of the pivot bolt 48 and through which extends a retainer pin or bolt 50 that is screw threaded into the cross bar 35, said slot 49 and pin or bolt Si) cooperating to limit pivotal movement of the yoke 47 about the axis of the pivot bolt 48. A coil compression spring 51 is interposed between one end portion of the yoke 47 and the adjacent end of the brace bar 4G to yieldingly urge the yoke 47 in one direction of its pivotal movement. An adjustment screw 52 extends generally longitudinally of the rocking frame 35 and is screw threaded through the opposite end portion of the brace bar 40, and has abutting relationship with the end portion of the yoke 47 opposite the spring Si., whereby to move the yoke 47 in the opposite direction of its swinging movement against yielding bias of the spring 51. Thus, when an endless exible sanding band or belt, indicated by the numeral 53, is entrained over the contact roll 41 and the idler roll 44, manipulation of the adjustment screw 52 will cause the sanding belt 53 to properly track over the Contact and idler rolls 41 and 44 respectively.

The rocking frame 35 is mounted on the relatively fixed base frame 1 for pivotal movements o-n a horizontal axis extending parallel to the axes of the feed roller 22 and the contact roll 41 and the idler roll 44, by means of a relatively large diameter primary pivot element S4 journaled in a xed bracket 55 welded or otherwise secured to the upper edge of the side frame member 3 of the base frame 1, and a smaller diameter secondary pivot element or shaft S6 mounted in a bracket 57 operatively associated with the side frame member 4 of the base frame 1. As shown in Figs. 1 and 2, the bracket 57 is mounted for vertical sliding movements in a guide frame 58 that is welded or otherwise secured to the side frame member 4. An adjustment screw S9 is screw threaded through the bottom portion 60 of the guide frame 58 and extends vertically into abutting relationship with the bottom of the bracket 57, and is manipulated to raise or lower the bracket 57 to cause proper alignment to be achieved between the axes of the feed ro-ller 22 and the contact roll 41. Preferably, the pivot shaft 56 is removable from engagement with its respective side element 37 of the rocking frame 35 and the bracket 57 to facilitate removal of the sand ing belt 53 when the same is worn, and replacement thereof over the contact and idler rolls 41 and 44 respectively. Removal of the pivot shaft 56 from engagement with its respective side element 37 of the rocking frame 35, causes the entire rocking frame to be supported solely by the relatively large pivot element or shaft 54. Although not shown, the large primary pivot element or shaft 54 is capable of limited rocking movements in a vertical direction in the bracket 55 so as to permit raising and lowering of the bracket 57 to a very limited degree. This is accomplished by the use of a well-known self-aligning bearing, notshown, but interposed between the pivot shaft 54 and its respective bearing bracket 55. With this arrangement the bracket 57 may be raised or lowered ,to enable the machine to accommodate a workpiece X which may be of slightly greater thickness at one longitudinal edge portion than at theother thereof.

For the purpose of imparting rotary movement to the contact roll 41 to cause the sanding belt 53 to move at relatively high speed with respect to the workpiece X being fed at relatively low speed through the machine, l pro.- vide a drive motor 61 and power transmission mechanism therebetween and the contact roll 41, now to be described. The primary pivot element or shaft 54 is provided with an axially outwardly extending, diametrically reduced shaft portion 62 on which is mounted for rotation a drive pulley 63 including a sheave section 64 and a smaller multiple sheave section 65. A second multiple sheave 66 is rigidly secured to the outer end of the contact roll shaft 42, and is operatively coupled to the multiple sheave section 65 by a plurality of endless drive belts 67. A drive belt 68 runs over the sheave section 64 of the pulley 63 and another pulley 69 mounted fast on the l ing frame 35, the distance therebetween and the multiple sheave or pulley 66 remains the same in all positions of rocking movement of the frame 35. Hence, the need for special belt tightening means for the belts 67 is virtually eliminated, and such tightening need only be done to compensate for wear.

Gravity bias is imparted to the rocking frame 35 forwardly of the axis of its rocking movement to urge the contact roll 41 into operative engagement with the underlying workpiece X interposed therebetween and the feed roller 22, by means of a pair of suitable elements in the i nature of weights 71 that are mounted for longitudinal sliding movements one each on a different one of a pair of guide rods 72 that extend longitudinally of the rocking frame 35. The guide rods 72 are mounted in spaced parallel relation to respective side elements 36 and 37 of the rocking frame 35 by front and rear legs 73 and 74 respectively, that are rigidly secured at their lower ends to opposite end portions of the side elements 36 and 3 7, Although the guide rods 72 are shown as being upwardly spaced from their respective side elements 36 and 37 of the rocking frame, it will be appreciated that the front and rear guide rod supporting legs 73 and 74 may be disposed to project laterally outwardly from their respective side elements 36 and 37, whereby to facilitate removal or replacement of the sanding belt 53. It will be noted further that shifting of the weights 71 forwardly with respect to the machine will increase the bias irnparted to the contact roll 41 in the direction of the workpiece X while shifting of the weights 71 forwardly with respect to the machine will increase the bias imparted to the contact roll 41 in the direction of the workpiece X while shifting of the weights 71 rearwardly will cause a decrease of said yielding bias. Hence, with this arrangement, an operator is enabled to adjust the pressure of the sanding belt 53 upon the workpiece X to obtain the desired finish, and the amount of material to be removed from the workpiece X can be controlled with a high degree of accuracy. For the purpose of releasably locking the weights 71 in desired set positions on the guide rods 72, I provide releasable locking means in the nature of set screws or the like 75 screw-threaded into each of the weights 71, the inner ends of the set screws being engagable with portions of the guide rods 72 ex tending through central passages in the weights 71. For limiting downward movement of the contact roll 41 and preventing the sanding belt 53 from coming into contact with the feeding roller 22, l provide stop screws 76 which are screw-threaded through outwardly projecting lugs 77 on the front ends of the side elements 36 and 37. The stop screws 76 extend downwardly from the lugs 77 and are adapted to have abutting engagement with stop lugs or ears 78 which project rearwardly from the front brackets 16. The stop screws 76 are utilized to positively limit the depth of cut made by the sanding belt 53 into the material X. This is particularly important when sanding a workpiece X which has a very thin veneer surface to be sanded. When sanding such material it is desirable that the sanding belt 53 engages the material of the workpiece X with an extremely light pressure. This, as above indicated, is achieved by the location of the weights 71 on the guide rods 72, and the maximum depth of cut is determined by the setting of the stop screws 76.

The sand in belt 53 is preferably made from paper with abrasive material cemented or otherwise adhered to the outer surface thereof. The speed of the motor 61 and the characteristics of the power transmission mechanism therebetween and the contact roll 41 are such, that the sanding belt 53 operates at speeds between 3,000 and 6,000 linear feet per minute. Under a no-load operating condition of the machine, manipulation of the adjustment screw 52 is usually sufficient to cause the belt 53 to track properly over the contact roll 41 and the idler roll 44. However, when a workpiece X is introduced between the feed roller 22 and the overlying belt-equipped contact roll 41, an unbalanced system results, causing the belt 53 to move laterally toward one end or the other of the rolls 41 and 44. This is particularly true when a relatively narrow workpiece X is passed through the machine at one side or other of the longitudinal center of the sanding belt 53. Moreover, the sanding belt, being made of relatively thin paper or the like, is caused to stretch to a limited degree over its work engaging area. This stretch being unevenly disposed over the entire area of the sanding belt 53 also aids in causing the same to move laterally in the machine.

For the purpose of causing the belt 53 to properly track over the contact and idler rolls 41 and 44 respectively when a work load is applied to the sanding belt 53, I provide a pair of elongated pulleys 79 that are journaled each on one leg of a pair of generally U-shaped supporting brackets 80 for rotation on axes extending generally transversely of the rocking frame 35. Each of the U-shaped brackets 80 is pivotally secured to a different one of the side elements 36 and 37 of the rocking frame 35 for swinging movements about an axis extending generally longitudinally of the rocking frame 35. A

pivotal mounting for the U-shaped brackets is shown75 in Fig. 5, said pivotal mounting including a nut-equipped pivot bolt 81 extending through one leg of the bracket 80 and through a suitable mounting ear or lug 82, fast on its respective side element. With reference to Fig. l, it will be seen that the sanding belt 53 defines an approach light A to the contact roll 41 and a departure flight B therefrom. It will be further noted that the pulleys 79 are disposed in closely spaced relation to the contact roll 41 and positioned to engage the relatively smooth under-surface of the belt 53 in its approach flight A. v

If, for example, during operation of the machine, the sanding belt 53 is caused to move from the left to the right with respect to Fig. 3, the right hand pulley 79 is caused to move from its normal dotted line positionof Fig. 5 to its full line position of Fig. 5, thus causing entrainment by the pulley 79 of a relatively wide portion of the belt 53, and causing the same to move to the left with respect to Figs. 3 and 5. The pulley at the left hand side of the machine, as seen in Fig. 3, operates in the same manner to stop undue movement of the sanding belt 53 in a left hand direction and cause the same to move to its central position of Fig. 3. The pulleys 79 and mounting means therefor is disclosed, together with a complete description of the operation thereof in my co-pending United States application, Serial No. 481,808,

led January 14, 1955, now Patent No. 2,813,382, dated` November 19, 1957, and entitled Sanding Machine and Method of Preventing Belt Creeping. The structure of the pulleys and the U-shaped brackets 80 therefor differs. from that shown in my co-pending application, above identified, only in the construction of the bracketsy 80. In the present machine, I provide each bracket 80 with a laterally outwardly projecting stem 83 on which lare mounted counterbalancing elements or weights 84. The weights 84 are so located on their respective stems 82, that the mounting brackets 80 and their respective pulleys 79 are maintained substantially in a state of equilibrium. Thus, a minimum of pressure applied to the pulleys 7 9 adjacent edges of the sanding belt A, when the same moves laterally from its normaltrack, is required to move the pulleys to their belt-entraining full line positions indicated in Fig. 5.

While I have shown and described a commercial ernbodiment of my sanding machine, it will be understood that the same is capable of modification without departure from the spirit and scope of the invention as dened in the claims.

What I claim is:

1. In a sanding machine, a relatively fixed base frame. means including a power driven feed roller journaled to said base frame for feeding a workpiece in a direction generally normal to the axis of the feed roller, a generally rectangular rocking frame, means including axially aligned primary and secondary pivots intermediate the ends of said rocking frame and mounting said rocking frame on said base frame for rocking movements ony an axis parallel to the axis of said feed roller, said pri mary and secondary pivots comprising primary and secondarypivot shafts respectively at opposite sides of said rocking frame, a contact roll journaled to an end portion of said rocking frame in overlying generally parallel spaced relation to said feed roller and movable in a generally vertical direction toward and away from said feed roller upon rocking movements of said rocking frame, an idler roll journalled at the opposite end portion of said rocking frame on an axis substantially parallel to the axis of said contact roll, a wide endless workengaging sanding belt entrained over said rolls, said rocking frame being yieldingly biased in a direction to urge the contact roll toward the feeding roller and interposed workpiece, and mechanism for imparting rotation to said contact roll, said mechanism comprising, a motor, drive pulley means coaxial with and adjacent said primary pivot and operatively coupled to said motor, and driving 7 connections between said drive pnlleyv means and said contact' roll, said secondary shaft being r'eleasably connected to one of said frames and being removable therefrom to permit entranment of said sanding belt' over saidE contact and idler roll.

2'. In a sanding machine, a relatively xed base frame, means including a power driven feed roller journaled to said base frame for feeding a workpiece in a direction generally normal tothe axis of the feed roller, a generally rectangular rocking frame, a primary pivot intermediate the ends of said rocking frame at one side thereof mounting said rocking frameV on said base frame for rocking movements on an axis parallel to the axis of said feed roller, a secondary pivot comprising. ak pivot shaft at the opposite sideI of said rocking frame in axial alignment with said primary pivot, a supporting, bracket for said secondary pivot shaft, means defining guide- Ways on said base framev mounting said supporting bracket for movements relative to said base frame to move said secondary pivot shaft toward and away' from axial alignment with said primary pivot, adjustment means for imparting said movementto` said supporting bracket', a contact roll journaledL to one end portion ot' said rocking frame in overlying generally parallel spaced relation to said feed roller and movable in a vertical direction to'- Ward and awayl from said feed roller upon rocking move'- ment's of said rocking frame on the axis of said pivots, an idler roll journalled at the opposite endl portion of said rocking frame on an axis substantially parallel to the axis of said Contact roll, a Wide endless work-engagingy sanding belt entrained over said rolls, said rocking frame being yieldingly biased in a direction to urge the contact roll toward the feeding roller and interposed workpiece, and mechanism for imparting rotation to said contact roll, said mechanism comprising a motor and driving connections between said motor and contact roll.

References Cited in the tile of this patent UNITED STATES PATENTS 1,100,801 Wendell June 23, 1914 1,437,414 Gruenhagen Dec. 5, 1922 2,012,163 Gauld Aug. 20, 1935 2,257,305 Nickerson Sept. 30, 1941 2,507,372 Emmons May 9, 1950 

